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根据农业系统工程学“最佳模拟配合法”原则，采用二次旋转组合回归设计，探讨了在半干旱地区立地条件下，可控因子（播种密度、氮肥施用量、磷肥施用量、磷酸二氢钾根外追肥用量和磷酸二氢钾根外追肥时间）对胡麻籽粒的增产效应，通过计算机模拟选优确立了两套旱地胡麻籽粒亩产大于90kg的优化方案。 相似文献
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旋转悬臂输流直管,结合了输流管道和旋转梁的工作特点,在旋转装置中应用广泛,其振动现象对系统的稳定性和可靠性有着重要的影响。针对旋转悬臂输流直管,采用哈密顿方法推导了旋转悬臂输流直管的线性振动微分方程,应用小波有限单元法离散微分方程,构建了旋转悬臂输流直管面内和面外振动的小波单元矩阵。通过分析面内和面外振动的临界流速,表明转速能够增大临界流速曲线的稳定区域,对于质量比相同时,面外的临界流速大于面内的,且随着转速的增大,面内面外的临界流速差值增大。在流速不断增大时,面内振动先于面外发生失稳,对于含有充液管道的旋转机械设计有着参考价值。 相似文献
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在卧式铣床上加工大螺旋角(大于45°)的工件如加工大螺旋角螺旋槽和斜齿轮时，由于受机床本身工作台角度旋转的限制，往往需要进行相关的机床调整和挂轮计算。我们知道，在铣床上铣削加工时，工件一般要完成如下运动：随工作台纵向进给作匀速直线运动；装夹在分度头卡盘内作匀速旋转；铣完一个槽(齿)后要作分度分槽(齿)。为此，机床纵向工作台和分度头的传动系统要做相应的调整，使纵向进给丝杠带动纵向工作台移动的同时，又经挂轮带动分度头使工件作匀速旋转，以实现刀具与工件的相对运动，最终加工出所需的工件。机床纵向工作台和分度头的… 相似文献
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选择焦点和焦点参数为基本量，将几何光学中只研究球面成像，扩展到旋转二次曲面成像、研究了旋转二次曲面及其透镜的成像规律和成像质量等问题，展现了研制各种旋转二次曲面透镜的必要性，为光学仪器的改进和更新换代奠定了理论基础、将旋转二次曲面的成像理论引入了几何光学教学和新的几何光学教材中。从只研究球面成像扩展到整个旋转二次曲面，从而扩大了学生的知识面，培养了学生的科研能力和创造思维能力。 相似文献
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马吉超 《中学数学教学参考》2005,(9):25-26
一个图形围绕某一点由一个位置转到另一个位置的运动叫旋转，这个点叫旋转中心，确定图形旋转的三个要素是：旋转中心、旋转方向、旋转角度，图形旋转的主要特征是：图形中每一点都绕着旋转中心旋转了同样大小的角度，对应点到旋转中心的距离相等，对应线段相等，对应角相等，图形的形状与大小没有发生变化。 相似文献
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《嘉应学院学报》2017,(5):22-26
梅州金柚包含了早熟品种蜜柚与晚熟品种沙田柚.在基于图像处理的金柚检测研究工作中,将金柚图像旋转至适宜图像检测的摆放角度,是实现高质量检测的前提.在金柚图像旋转校正工作中,采用Sobel算子提取金柚轮廓,并计算各轮廓点的方向角度;利用金柚纵径与横坐标垂直时底部轮廓呈水平线状的特点,在旋转过程中对金柚底部区域方向角度大于85°的轮廓像素点,并以其最大值所对应的旋转角度作为最佳校正角度.为验证算法的有效性,选取213幅金柚图像样品做旋转校正实验,近90%样品旋转校正角度的绝对误差落入5°范围之内,旋转校正结果令人满意.该方法对于后续的金柚尺寸测量,三维抓取研究具有重大意义. 相似文献
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新课程标准下的初中数学教材中，删去了原三角形全等部分的知识，增加了平移、旋转的内容。使得数学更贴近生活。解题方法更灵活多变，为帮助同学们把握好平移、旋转的特征，巧妙地利用平移和旋转的知识来解决有关问题，本文举例如下： 相似文献
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侯国兴 《语数外学习(初中版)》2007,(9X):24-25
我们知道旋转图形具有以下特征：（1）图形中的每一点都绕着旋转中心旋转了同样大小的角度；（2）对应点到旋转中心的距离相等；（3）对应角、对应线段相等；（4）图形的形状和大小都不变．利用旋转的特征，我们可以巧妙地解决很多几何问题，现举例如下．[第一段] 相似文献
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《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
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罗艳萍 《读与写:教育教学刊》2008,5(6)
The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity. 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献
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Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
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Richard Denner 《海外英语》2007,(4):14-15
Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose. 相似文献
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Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 相似文献
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RUZBEHANI Mohsen 《重庆大学学报(英文版)》2004,3(1):20-25
1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec… 相似文献